Method And Apparatus For Tool Retrieval

ABSTRACT

The present disclosure is directed towards, in general, retrieval tools operable for conveyance within a wellbore extending below a wellsite surface, and methods of using such retrieval tools. One such retrieval tool comprises an annular member operable to receive a conveyance terminating at a downhole tool lodged within the wellbore. The annular member may subsequently receive and engage a portion of the downhole tool. The retrieval tool also comprises a flapper selectively operable to sever the conveyance if the downhole tool cannot be dislodged from the wellbore.

BACKGROUND OF THE DISCLOSURE

In a variety of well-related operations, downhole tools are utilized to carry out desired tasks at downhole locations. For example, different types of downhole tools may be utilized to drill wellbores, deploy tubing and other equipment downhole, perform testing operations, and conduct servicing operations, among other possibilities. During these operations, a downhole tool may become lodged in the wellbore or disconnected from its conveyance. The lodged tool may be referred to as a fish, and a fishing operation may be performed in an attempt to retrieve the fish. For example, a fishing tool may be deployed downhole from a surface rig or platform. The fishing tool comprises a latching or attachment end intended to engage the fish to be retrieved. If the fish cannot be dislodged from the wellbore, the fishing tool is removed from the well. Another downhole tool may then be deployed to separate the fish from its conveyance, such that the conveyance may be retrieved to surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 is a schematic view of at least a portion of apparatus according to one or more aspects of the present disclosure.

FIG. 2 is a schematic view of at least a portion of apparatus according to one or more aspects of the present disclosure.

FIG. 3 is a schematic view of at least a portion of apparatus according to one or more aspects of the present disclosure.

FIG. 4 is a schematic view of at least a portion of apparatus according to one or more aspects of the present disclosure.

FIG. 5 is a schematic view of at least a portion of apparatus according to one or more aspects of the present disclosure.

FIG. 6 is a schematic view of at least a portion of apparatus according to one or more aspects of the present disclosure.

FIG. 7 is a schematic view of at least a portion of apparatus according to one or more aspects of the present disclosure.

FIG. 8 is a schematic view of at least a portion of apparatus according to one or more aspects of the present disclosure.

FIG. 9 is a schematic view of at least a portion of apparatus according to one or more aspects of the present disclosure.

FIG. 10 is a flow-chart diagram of at least a portion of a method according to one or more aspects of the present disclosure.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact.

An overshot is a type and/or portion of a fishing or other retrieval tool and/or tool string that may utilized in fishing operations to engage a surface and/or other portion of a tube or downhole tool that has become lodged downhole. Fishing may comprise attempting to grip and/or otherwise engage the fish via a grapple and/or other slip mechanism of the overshot, thus allowing the application of tensile and/or jarring forces intended to dislodge the fish. The fish may comprise a “fishing neck” and/or other member or surface intended to aid engagement between the fish and the fishing tool. If the fish cannot be removed, a release mechanism of the overshot may allow the overshot to be disengaged from the fish and retrieved to surface.

Fishing tools may generally fall into four classes: diagnostic, inside grappling, outside grappling, and force intensifiers or jars. Diagnostic devices may range from a simple impression block made in a soft metal (e.g., lead) that may be dropped rapidly onto the top of the fish so that, upon inspection at the surface, the surface operator (or “fisherman”) may be able to custom design a retrieval tool to facilitate attachment to and removal of the fish. Other diagnostic tools may include electronic instruments and/or downhole sonic or visual-bandwidth cameras. Inside grappling devices (which may be referred to as “spears”) may have a tapered and threaded profile, enabling the fisherman to first guide the tool onto the top of the fish, and then thread the fishing tool into the top of the fish so that recovery may be attempted. Outside grappling devices (referred to herein as “overshots”) may comprise an annular member that “swallows” the fish and does not release it as it is pulled out of the wellbore. One or more aspects of the present disclosure may be applicable or readily adaptable to any of the apparatus described above, as well as operations involving such apparatus.

The present disclosure introduces an apparatus comprising: a retrieval tool operable for conveyance within a wellbore extending below a wellsite surface, wherein the retrieval tool comprises: an annular member operable to receive a conveyance terminating at a downhole tool lodged within the wellbore, and then receive and engage a portion of the downhole tool; and a flapper operable to sever the conveyance. The flapper may be spring-loaded or otherwise biased towards an open position permitting passage of the conveyance. The wellbore may comprise a substantially horizontal and/or otherwise substantially non-vertical section. The conveyance may comprise a cable and/or coiled tubing extending between the wellsite surface and the downhole tool. The cable may comprise a wireline and/or a slickline.

The present disclosure also introduces an apparatus comprising: a fishing string operable for conveyance within a wellbore extending below a wellsite surface, wherein the fishing string comprises: a mule shoe operable to receive a conveyance terminating at a downhole tool lodged within the wellbore, and then to receive a portion of the downhole tool; an overshot operable to receive the conveyance, and then to receive and engage a portion of the downhole tool; and a flapper assembly operable to sever the conveyance. The flapper assembly may be biased towards a position permitting passage of the conveyance therein. The conveyance may comprise a cable and/or coiled tubing extending between the wellsite surface and the downhole tool. The cable may comprise a wireline and/or a slickline.

The present disclosure also introduces a method comprising: conveying a retrieval tool along a conveyance within a wellbore extending into a subterranean formation; utilizing the retrieval tool in an attempt to engage and retrieve a downhole tool in the wellbore; and severing the conveyance with the retrieval tool downhole upon failure of the attempt. Conveying the retrieval tool along the conveyance may comprise conveying the retrieval tool on a pipe string to which the retrieval tool is coupled. Conveying the retrieval tool along the conveyance may comprise sliding the retrieval tool and the pipe string over the conveyance. The conveyance may comprise a cable extending between the downhole tool and a well-site surface from which the wellbore extends. The cable may comprise a wireline and/or a slickline. The conveyance may comprise coiled tubing extending between the downhole tool and a well-site surface from which the wellbore extends. Severing the conveyance with the retrieval tool may comprise selectively operating a flapper assembly of the retrieval tool. Conveying the retrieval tool along the conveyance within the wellbore may comprise passing the conveyance through the flapper assembly. Severing the conveyance with the retrieval tool may comprise closing the flapper on the conveyance with sufficient force to sever the conveyance. Closing the flapper may comprise pumping fluid down the wellbore from a well-site surface from which the wellbore extends. The flapper may be mechanically biased towards an open position, and pumping fluid down the wellbore from the well-site surface may comprise pumping the fluid at a rate sufficient for the fluid to overcome the mechanical bias and urge the flapper away from the open position.

An example fishing string 100 comprising an overshot 110 according to one or more aspects of the present disclosure is depicted in FIG. 1. The fishing string 100 is suspended in the wellbore 105 via a wireline, slickline, pipe, and/or other conveyance 120. The fishing string 100 may also comprise an accelerator 130, a section of pipe or pipe string 140, a jar 150, and/or a bumper sub 160. The order of the components of the fishing string 100 may vary from that shown in FIG. 1, and the fishing string 100 may comprise fewer components than those depicted in FIG. 1, as well as additional components not otherwise described herein.

The accelerator 130 and/or the jar 150 may store energy that is suddenly released upon activation. While there are two primary types of accelerators and jars (hydraulic and mechanical), their operation is similar. For example, energy is stored in the conveyance 120 and/or other components of the fishing string 100, and this energy is suddenly released upon activation of the accelerator 130 and/or the jar 150. The principle is similar to that of a carpenter using a hammer. Kinetic energy stored in the hammer as it is swung is suddenly released to the nail and board when the hammer strikes the nail. When utilizing the accelerator 130 and/or the jar 150, the fisherman may pull up on the conveyance 120, but the fish 170 does not move. Since the top of the conveyance 120 (at surface) is moving upward, the conveyance 120 is stretching and storing energy. Upon activation, a dynamic portion of the jar 150 rapidly translates in an uphole direction until slamming into a shoulder or stop of a static portion the jar 150, thus imparting an impact force to the static portion of the jar 150, which is mechanically transferred to the fish 170 via the overshot 110 and/or other components of the fishing string that may be positioned between the jar 150 and the fish 170. The accelerator 130 may similarly impart such an impact. The impact force applied to the fish 170 in this manner may aid in the release of the fish 170 engaged by the overshot 110.

The section of pipe or pipe string 140 may be included in the fishing string 100 to increase the mass suddenly propelled in an uphole direction upon activation of the accelerator 130 and/or the jar 150, and/or to provide sufficient weight acting downward on the accelerator 130 and/or the jar 150 such that they may be reset in preparation for a subsequent activation. The bumper sub 160 may be included as a mechanical buffer or the like, such as may lessen the likelihood of the fish 170 being damaged by the impact force imparted by activation of the accelerator 130 and/or the jar 150.

An overshot, fishing tool, and/or other retrieval tool (collectively referred to hereafter as simply “retrieval tool”) according to one or more aspects of the present disclosure may be fed over the conveyance and deployed downhole to engage the fish. Such operation may utilize a “cut and thread” method, in which the conveyance is gripped and cut at surface. The cut end is threaded through one or more joints or stands of pipe and/or other means of conveying the retrieval tool (hereafter collectively referred to as “pipe” for the sake of simplicity), which are then lowered and temporarily suspended in the wellbore. The conveyance is then threaded through another one or more joints or stands of pipe, which are then coupled to the pipe suspended in the wellbore. This process is repeated until the retrieval tool at the lower end of the pipe suspended in the wellbore can no longer be translated further into the borehole, either because the retrieval tool has reached the fish, or because the retrieval tool itself has become lodged in the wellbore at a depth shallower than the fish.

Thus, in certain situations, the retrieval tool may not be able to engage or subsequently dislodge the fish. Accordingly, retrieval tools within the scope of the present disclosure also comprise a flapper assembly that may be utilized to cut the conveyance as close to the fish as possible to allow retrieval of a substantial portion of the conveyance. Thus, retrieval tools according to one or more aspects of the present disclosure may enable retrieval of the fish by engagement of the fish with the retrieval tool and, if the fish cannot be retrieved, retrieval of at least a portion of the conveyance by cutting the conveyance with the flapper assembly. Retrieval tools within the scope of the present disclosure may be utilized in various downhole operations, including within wellbores that comprise one or more substantially horizontal or otherwise substantially non-vertical portions, in which conveying the retrieval tool to the fish may be difficult using traditional, gravity-fed techniques.

FIG. 2 is a schematic view of at least a portion of an implementation of the fishing string 100 shown in FIG. 1 according to one or more aspects of the present disclosure. The illustrated portion includes a retrieval tool 200, a mule shoe 202, and an overshot 204 coupled between the retrieval tool 200 and the mule shoe 202. The retrieval tool 200, the mule shoe 202, and the overshot 204 may be coupled as shown in FIG. 2 via industry-standard box-pin connections, among other means within the scope of the present disclosure. A wireline, slickline, coiled tubing, and/or other conveyance 206, depicted as extending through the retrieval tool 200, the overshot 204, and the mule shoe 202, may be connected to a fish (not shown).

FIG. 3 is an enlarged view of the retrieval tool 200 shown in FIG. 2. The retrieval tool 200 may comprise a housing 210 extending between an upper sub 220 and a lower sub 230. The upper and lower subs 220 and 230 may be coupled within the fishing string via industry-standard box-pin connections, among other means within the scope of the present disclosure. A sleeve 240, a flapper assembly 250, and a biaser 260 may be disposed within the housing 230. The flapper assembly 250 is depicted in an open position in FIG. 2 and in a closed position in FIG. 3.

FIG. 4 is an enlarged view of a portion of the retrieval tool 200 shown in FIG. 2. The flapper assembly 250 is depicted in FIG. 4 as being in an open position, such that the conveyance 206 extending through the retrieval tool 200 may also extend through the flapper assembly 250.

Operations utilizing the retrieval tool 200 will now be described with reference to FIGS. 2-4, collectively. During fishing operations, the cut and thread method described above may be utilized to convey the retrieval tool 200 towards the fish (not shown). During the cut and thread method, or any other method utilized to convey the retrieval tool 200 within the wellbore, the conveyance 206 will pass through the mule shoe 202, the overshot 204, and the retrieval tool 200, including through the flapper assembly 250. The biaser 260 may enable pipe movement in the upward direction, such as during unsetting and setting the slips, without inadvertently affecting the flapper assembly 250. After the retrieval tool 200 is fed downhole over the conveyance 206 to the fish, the surface operator may attempt to engage the fish with the overshot 204 and pull the fish out of the wellbore. If it is not possible to engage the fish with the overshot 204, the surface operator may apply pressure or overpull such that the flapper assembly 250 may sever the conveyance 206. The option of severing the conveyance 206 may be a secondary to retrieving the fish, but it may nonetheless be a better option relative to leaving the entire conveyance 206 within the wellbore. Moreover, by utilizing a retrieval tool according to one or more aspects of the present disclosure, the conveyance 206 may be severed from the fish as part of a single retrieval operation, instead of pulling the retrieval tool out of the wellbore and then inserting a separate cutting tool into the wellbore to sever the conveyance 206.

The biaser 260 depicted in the figures comprises a helical compression spring coupled and/or extending between the flapper assembly 250 and the lower sub 230. However, other means for permitting axial translation of the retrieval tool 200 relative to the fish without inadvertently severing the conveyance 206 are also within the scope of the present disclosure.

As depicted in FIG. 4, the flapper assembly 250 may maintain an open position as the retrieval tool 200 travels down the conveyance 206 toward the fish. In some scenarios, as described above, if the fish cannot be retrieved, the conveyance 206 may be severed before the retrieval tool 200 is returned to surface. For example, fluid may be pumped from surface down through the retrieval tool 200. The fluid may comprise drilling fluid (“mud”), hydraulic fluid, fracturing fluid, and/or other fluids. The flow of such fluid may act on the flapper assembly 250 to move the flapper 255 away from the inside wall of the sleeve 240, thus partially closing the flapper assembly 250 and partially engaging the conveyance 206 between the flapper 255 and a base 257 of the flapper assembly 250. This partially closed position of the flapper 255 is depicted in FIG. 5. The retrieval tool 200 is then moved in an uphole direction and, because the conveyance 206 remains attached to the fish below the retrieval tool 200, the flapper 255 will further close on the conveyance 206 until, with sufficient uphole movement of the retrieval tool 200, the flapper assembly 250 will sever the conveyance 206. The closed flapper assembly 250, after having severed the conveyance 206, is depicted in FIG. 6.

FIG. 7 is a schematic view of an implementation of the flapper assembly 250 described above, and depicted as being oriented in a partially open configuration. FIG. 8 is a sectional view of the flapper assembly 250 shown in FIG. 7, but in a closed configuration. FIG. 9 is a top view of the flapper assembly 250 shown in FIGS. 7 and 8, where the flapper assembly 250 is depicted in an open configuration. Referring to FIGS. 7-9 collectively, the flapper 255 may be rotationally coupled to the base 257 by a hinge 310. The hinge 310 may comprise a flange 320 coupled to and extending from the base 257, and a member 330 extending through the flange 320 and the flapper 255. The member 330 may be a substantially cylindrical pin, such as may be press-fit within corresponding holes 340 in the flange 320 and extending through a corresponding hole in the flapper 255. However, other methods of rotationally coupling the flapper 255 to the base 257 are also within the scope of the present disclosure.

The flapper 255 may be biased towards an open position. For example, the flapper assembly 250 may comprise one or more torsion springs and/or other means (not shown) intended to bias the flapper 255 away from the closed position shown in FIG. 8. However, such biasing means may not be included, such that the flapper 255 may be urged away from the closed position merely by the existence of the conveyance 206 extending through the opening or other passage 350 of the base 257. By including the passage 350 in the base 257, the base 257 may be considered an annular member to which the flapper 255 is rotationally coupled.

The flapper 255 may comprise a closure portion 360 and a flange 370 extending centrally from the closure portion 360. The flange 370 may have a top edge or surface 375 sized to prevent the flapper 255 from rotating to a substantially vertical orientation parallel with the longitudinal axis of the retrieval tool 200. Thus, at its fully open position, as shown in FIG. 9, the closure portion 360 and/or the flange 370 may form one or more pockets 380 and/or other areas intended to react to the flow of fluid and thereby urge the flapper 255 towards the closed position shown in FIG. 8.

The flapper assembly 250 may be coupled within and/or otherwise to the sleeve 240 shown in FIGS. 1-6 and 9. The sleeve 240 and flapper assembly 250 may be able to axially float relative to the housing 210 depending on whether the flapper 255 is engaged with the conveyance 206 during the above-described severing operation. The sleeve 240 may also comprise one or more openings 390 permitting the passage of fluid flow into the annulus defined between the fishing string and the wellbore.

The various components of the retrieval tool 200, including those of the flapper assembly 250, may comprise one or more steel materials commonly utilized in the downhole environment. However, other substantially rigid materials are also within the scope of the present disclosure.

FIG. 10 is a flow-chart diagram of at least a portion of an example method 700 according to one or more aspects of the present disclosure. The method 700 may be performed utilizing the apparatus shown in FIGS. 1-9 and/or otherwise within the scope of the present disclosure.

The method 700 comprises the attempted retrieval (710) of the fish utilizing the retrieval tool 200 described above and/or other retrieval tools according to one or more aspects of the present disclosure. The method 700 also comprises a subsequent determination (720) of whether the fish has been successfully dislodged from the wellbore. If it is determined that the fish has been successfully dislodged, then the retrieval tool, the dislodged fish, and the conveyance coupled to the fish may be returned (730) to surface.

However, if it is determined that the fish has not been successfully dislodged from the wellbore, then the conveyance coupled to the fish may be severed (740) from the fish, such as by actuating the flapper assembly 250 described above. The retrieval tool and the severed conveyance may then be returned (750) to surface, abandoning the fish downhole.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure.

The Abstract at the end of this disclosure is provided to comply with 37 C.F.R. §1.72(b) to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 

What is claimed is:
 1. A method, comprising: conveying a retrieval tool along a conveyance within a wellbore extending into a subterranean formation; utilizing the retrieval tool in an attempt to engage and retrieve a downhole tool in the wellbore; and severing the conveyance with the retrieval tool downhole upon failure of the attempt.
 2. The method of claim 1 wherein conveying the retrieval tool along the conveyance comprises conveying the retrieval tool on a pipe string to which the retrieval tool is coupled.
 3. The method of claim 2 wherein conveying the retrieval tool along the conveyance comprises sliding the retrieval tool and the pipe string over the conveyance.
 4. The method of claim 1 wherein the conveyance comprises a cable extending between the downhole tool and a well-site surface from which the wellbore extends.
 5. The method of claim 4 wherein the cable comprises at least one of a wireline and a slickline.
 6. The method of claim 1 wherein the conveyance comprises coiled tubing extending between the downhole tool and a well-site surface from which the wellbore extends.
 7. The method of claim 1 wherein severing the conveyance with the retrieval tool comprises selectively operating a flapper assembly of the retrieval tool.
 8. The method of claim 7 wherein conveying the retrieval tool along the conveyance within the wellbore comprises passing the conveyance through the flapper assembly.
 9. The method of claim 8 wherein severing the conveyance with the retrieval tool comprises closing the flapper on the conveyance with sufficient force to sever the conveyance.
 10. The method of claim 9 wherein closing the flapper comprises pumping fluid down the wellbore from a well-site surface from which the wellbore extends.
 11. The method of claim 10 wherein the flapper is mechanically biased towards an open position, and wherein pumping fluid down the wellbore from the well-site surface comprises pumping the fluid at a rate sufficient for the fluid to overcome the mechanical bias and urge the flapper away from the open position.
 12. An apparatus, comprising: a retrieval tool operable for conveyance within a wellbore extending below a wellsite surface, wherein the retrieval tool comprises: an annular member operable to receive a conveyance terminating at a downhole tool lodged within the wellbore, and then receive and engage a portion of the downhole tool; and a flapper operable to sever the conveyance.
 13. The apparatus of claim 12 wherein the flapper is biased towards an open position permitting passage of the conveyance.
 14. The apparatus of claim 12 wherein the wellbore comprises a substantially non-vertical section.
 15. The apparatus of claim 12 wherein the conveyance comprises a cable extending between the wellsite surface and the downhole tool.
 16. The apparatus of claim 12 wherein the conveyance comprises coiled tubing extending between the wellsite surface and the downhole tool.
 17. An apparatus, comprising: a fishing string operable for conveyance within a wellbore extending below a wellsite surface, wherein the fishing string comprises: a mule shoe operable to receive a conveyance terminating at a downhole tool lodged within the wellbore, and then to receive a portion of the downhole tool; an overshot operable to receive the conveyance, and then to receive and engage a portion of the downhole tool; and a flapper assembly operable to sever the conveyance.
 18. The apparatus of claim 17 wherein the flapper assembly is biased towards a position permitting passage of the conveyance therein.
 19. The apparatus of claim 17 wherein the conveyance comprises a cable extending between the wellsite surface and the downhole tool.
 20. The apparatus of claim 17 wherein the conveyance comprises coiled tubing extending between the wellsite surface and the downhole tool. 